1. Field of the Invention
The present invention relates in general to an ink-jet recording apparatus, and more particularly to an ink-jet head unit of the ink-jet recording apparatus, which is provided with an ink-jet head and a flexible wiring board.
2. Discussion of Related Art
A known ink-jet recording apparatus uses four ink cartridges for cyan, magenta, yellow and black inks, for example, to perform a color printing operation. These ink cartridges are held by a head holder, which carries four ink-jet heads for ejecting the inks of the respective four colors, and circuit boards for driving these ink-jet heads. Each of the ink-jet heads and the corresponding circuit board are connected to each other through a flexible wiring board, to form an ink-jet head unit. Each ink-jet head is supplied with the corresponding color ink delivered from the corresponding ink cartridge, so that the ink is ejected from nozzles of the ink-jet head, to form a desired image on a recording medium.
The flexible wiring board is an electrically insulating flexible film of a generally rectangular shape having a wiring pattern including a multiplicity of conductive wires extending in its longitudinal direction. The flexible wiring board is widely used to install complicated electronic circuits in a relatively small space. In the ink-jet recording apparatus, the electrical connection between the ink-jet head and the flexible wiring board is made by soldering or otherwise joining the terminals of the ink-jet head and the terminal lands of the flexible wiring board to each other
The soldered or otherwise joined portion of the ink-jet head unit has a comparatively low mechanical strength in the direction of separation of the terminals, and tends suffer from a risk of poor or faulty electrical connection or electrical discontinuity at the joined portion due to the separation or removal of the terminals and the terminal lands from each other, which separation takes place when a force acts between the ink-jet head and the flexible wiring board, in the direction of removal of the flexible wiring board from the ink-jet head. To prevent this drawback, a suitable reinforcement is conventionally provided to sandwich the joined portion, so as to increase the mechanical strength of the jointed portion in the direction of removal. Alternatively, small holes are formed through the flexible wiring board, so that these small holes are filled with a surplus amount of the molten solder, which is eventually solidified to reinforce the jointed portions. An example of this technique is disclosed in JP-8-32194A.
In the ink-jet head unit, however, the circuit board is disposed in an upper part of the ink-jet head, so that the flexible wiring board which connects the circuit board and the ink-jet head must be oriented such that a non-joined portion of the flexible wiring board at which the flexible wiring board is not joined to the ink-jet head extends obliquely upwardly from the ink-jet head toward the circuit board. In this orientation, the flexible wiring board tends to suffer from a problem of stress concentration at the corresponding ends of the joined and non-joined portions, and consequent separation of the joined portion from the ink-jet head